Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.37	13.651%	$256.1353	$256.14	$256.15	$256.10
Purchase #2	$189.43	7.511%	$203.6581	$203.66	$203.65	$203.70
Purchase #3	$47.90	13.416%	$54.3263	$54.33	$54.35	$54.30
Purchase #4	$248.43	5.527%	$262.1607	$262.16	$262.15	$262.20
Purchase #5	$147.67	11.802%	$165.098	$165.10	$165.10	$165.10
Purchase #6	$247.33	11.345%	$275.3896	$275.39	$275.40	$275.40
Purchase #7	$214.82	3.388%	$222.0981	$222.10	$222.10	$222.10
7 purchase totals =	$1,320.95		$1,438.8661	$1,438.88	$1,438.90	$1,438.90